Neither U.S. Secretary of State John Kerry nor Russian Foreign Minister Sergei Lavrov, who will meet in Moscow next week, plan to attend the Geneva meeting.

U.S. State Department spokesman John Kirby said Assistant Secretary of State Anne Patterson, the top U.S. diplomat for the Middle East, will represent Washington at the meeting, which he said will "try to get at the framework and the architecture for a cease-fire."

De Mistura told Reuters the talks are part of preparatory work "to better organize the future Vienna meetings."

Whether higher-level talks on Syria reconvene in New York later this month hinges on efforts currently under way in Saudi Arabia to unite Syrian opposition groups, ministers have said.

De Mistura said its too early to review the outcome of the opposition group meeting in Riyadh, which is still taking place.